Abstract

A qualitative model explanation of the experimentally obtained field dependences of the magnetization in ferro- and antiferromagnetic media in contact with one another is proposed. In this model a thin ferromagnetic(FM) film on an antiferromagnetic(AFM) substrate consists of only two ferromagnetic layers. This is the simplest model which admits a spatially nonuniform FM state. In this exactly solvable model it shown that a range of fields exists where a stable collinear (canted) structure of the FM subsystem obtains. This structure corresponds to inclined sections of the field dependence of the magnetization which are not associated with the kinetics of the magnetization reversal process. In the model proposed, for systems with large easy-plane anisotropy the magnetization reversal process with “exchange bias” taken into account is strictly symmetric as a function of the field provided that the additional weak FManisotropy in the easy plane is neglected. When this anisotropy in the easy plane is taken into account hysteresis appears in the magnetization curve and the field dependence becomes asymmetric.

Partial financial support for this work was provided by a contract for scientific collaboration between NASU (Ukraine) and CNRS (France), a grant from the Academy of Sciences of Ukraine on research into nanostructures, grant N 8-2009 for scientific collaboration between the National Academy of Sciences of Ukraine and RFFI Russia, a grant from the Royal Society of UK (Great Britain), and a grant from the Swedish Academy of Sciences.

Article outline:I. INTRODUCTIONII. THEORETICAL MODEL OF A BILAYER FERROMAGNETIII. FIELD DEPENDENCES OF THE MAGNETIZATION OF FERROMAGNETIC LAYERSIV. STABILITY OF MAGNETIC PHASES WITH DIFFERENT SYMMETRYV. EFFECT OF MAGNETIC ANISOTROPY IN THE EASY-PLANE ON THE FIELD DEPENDENCES OF THE MAGNETIZATIONVI. CONCLUSION